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排序方式: 共有139条查询结果,搜索用时 31 毫秒
61.
62.
DM Hidalgo RM Friendship L Greiner R Manjarín MR Amezcua JC Domínguez RN Kirkwood 《Reproduction in domestic animals》2014,49(6):899-902
The aim of this study was to determine the association between the oestrous response of pre‐pubertal gilts to gonadotrophin injection or boar exposure and their subsequent farrowing rate and litter size. At 154 days of age, randomly selected pre‐pubertal gilts received an intramuscular injection of 400 IU equine chorionic gonadotrophin plus 200 IU human chorionic gonadotrophin (PG600®; Merck Animal Health; n = 181). From the remaining pool of animals not treated with hormones, the first gilts showing signs of oestrus were selected to act as controls (n = 201). Boar exposure began at 155 days of age for both groups, and gilts were bred at a weight of approximately 130 kg. Comparisons were made between PG600®‐treated gilts exhibiting oestrus or not within 7 days post‐injection (early and late responders, respectively) and control gilts exhibiting oestrus or not within 30 days after beginning of boar exposure (select and non‐select control gilts, respectively). By 162 days, oestrus was detected in 67.5% of PG600®‐treated gilts compared with 5.7% of control gilts (p < 0.0001). The proportion of animals observed in oestrus at least three times before breeding was greater for select control gilts compared with early and late responder PG600®‐treated gilts (p ≤ 0.001). There were no significant differences in farrowing rate and litter size between the four treatment groups. These data indicate that PG600® is an effective tool to induce an earlier oestrus in gilts, that subsequent farrowing rate and born alive litter size compare favourably to that of select gilts and that gilts failing to respond promptly to hormonal stimulation do not exhibit compromised fertility. 相似文献
63.
R Manjarin G Cassar DJ Sprecher RM Friendship JC Dominguez RN Kirkwood 《Reproduction in domestic animals》2009,44(3):411-413
To meet weekly breeding targets, it is occasionally necessary to inject exogenous gonadotrophins to induce oestrus in prepubertal gilts. However, the gilt oestrus response to equine chorionic gonadotrophin (eCG) either alone or in combination with human chorionic gonadotrophin (hCG) can be unpredictable. The objective of the present study was to examine possible reasons for this unpredictability. Prepubertal gilts (90 kg and 153 days of age, n = 109) received an injection of either 600 IU eCG or a combination of 400 IU eCG and 200 IU hCG (PG600), or were non-injected controls, and were then exposed to a mature boar for 15 min daily for 7 days for oestrus detection. At the time of injection, real-time ultrasound revealed that the gilt ovaries had primarily 1–2 mm follicles. Blood samples were obtained at time of hormone injection (day 0) and at days 3, 7 and 10 for assay of serum progesterone concentrations. The oestrus responses by 7 days were15.5%, 73.3% and 0%, for eCG, PG600, and control gilts, respectively (p < 0.001). The oestrus response improved (p < 0.05) with increasing body weight. Based on circulating progesterone levels, all oestrous gilts ovulated except for four of the PG600 gilts. Failure to express oestrus in PG600 gilts was not associated with a premature rise in progesterone. 相似文献
64.
The effects of initial inoculum levels on spatio-temporal development in black rot of cabbage from artificial sources, one per plot, were evaluated in replicated field experiments. The results support the hypothesis that black rot is a polycyclic disease. Its development was inoculum-dependent because the progress rate of epidemics and spatial spread were both positively correlated with the strength of the source. Fast disease development was related to the number of rain days. The spread of black rot, associated with the primary gradient, at first resulted from allo-infection, later followed by a phase during which allo-infection was complemented by auto-infection. Three-dimensional maps of disease severity showed the dominance of the primary focus. Maximum distance of black rot symptoms from the source of the focus was limited to a few metres so that damage to cabbage by focal inoculum was limited to the plants close to the source. Spatio-temporal development and initial inoculum were related. High inoculum levels in point sources resulted in faster outward spread of black rot, and differences between low and high levels were generally significant. Under the conditions of the experiments, performed during three relatively dry seasons, a single source of infection measuring 0.5 × 0.5 m was not capable of spreading disease over all the plants in a plot of 6.5 × 6.5 m. The results imply that severe disease where whole crops are infected, as observed regularly in The Netherlands, can only originate from a large number of small foci per field. 相似文献
65.
66.
J. C. Zadoks 《Euphytica》1959,8(2):104-116
New physiologic races can be produced by mutation, hybridization or heterokaryosis. The genetics of the host parasite relationship can be explained on the basis of the gene-for-gene hypothesis of Flor. Resistance breeding is an important agent in the appearance of a new race and in the evolution of pathogenicity. In America the resistance breeding in wheat is conducted along the following lines:
- 1.Searching for sources of resistance by testing collections of varieties and hybrids. 相似文献
67.
PETR KLEMENT DVM CHRISTOPHER M. FEINDEL MD HUGH E. SCULLY MD EILEEN MESHER RN GIANNOULA KLEMENT BSc PEDRO DEL NIDO MD GREGORY J. WILSON MD 《Veterinary surgery : VS》1987,16(3):231-237
Although techniques for the perioperative management of patients undergoing mitral valve replacement have been well established in humans, the use of these techniques has not been widely accepted in veterinary practice. The purpose of this study is to demonstrate that low morbidity and mortality could be achieved in the dog undergoing mitral valve replacement. Nine mongrel dogs (25-45 kg body weight) were subject to left thoracotomy and mitral valve replacement using cardiopulmonary bypass (CPB). The average time on CPB was 1 hour with an aortic cross-clamping time of 40 minutes using chemically induced cardiac arrest. CPB was performed under conditions of moderate systemic hypothermia (28-30 degrees C) and hemodilution (hematocrit, 25-35%). Operative mortality was 22% (2/9) with one death from excessive bleeding and the other from cerebral air embolism. All other animals recovered and were clinically normal 3 weeks after surgery. The authors conclude that successful mitral valve replacement is possible in the large dog. 相似文献
68.
Host-response patterns of intramammary infections in dairy cows 总被引:2,自引:0,他引:2
Schukken YH Günther J Fitzpatrick J Fontaine MC Goetze L Holst O Leigh J Petzl W Schuberth HJ Sipka A Smith DG Quesnell R Watts J Yancey R Zerbe H Gurjar A Zadoks RN Seyfert HM;members of the Pfizer mastitis research consortium 《Veterinary immunology and immunopathology》2011,144(3-4):270-289
Many different bacterial species have the ability to cause an infection of the bovine mammary gland and the host response to these infections is what we recognize as mastitis. In this review we evaluate the pathogen specific response to the three main bacterial species causing bovine mastitis: Escherichia coli, Streptococcus uberis and Staphylococcus aureus. In this paper we will review the bacterial growth patterns, host immune response and clinical response that results from the intramammary infections. Clear differences in bacterial growth pattern are shown between bacterial species. The dominant pattern in E. coli infections is a short duration high bacteria count infection, in S. aureus this is more commonly a persistent infection with relative low bacteria counts and in S. uberis a long duration high bacteria count infection is often observed. The host immune response differs significantly depending on the invading bacterial species. The underlying reasons for the differences and the resulting host response are described. Finally we discuss the clinical response pattern for each of the three bacterial species. The largest contrast is between E. coli and S. aureus where a larger proportion of E. coli infections cause potentially severe clinical symptoms, whereas the majority of S. aureus infections go clinically unnoticed. The relevance of fully understanding the bovine host response to intramammary infection is discussed, some major gaps in our knowledge are highlighted and directions for future research are indicated. 相似文献
69.
Hotchkiss EJ Hodgson JC Schmitt-van de Leemput E Dagleish MP Zadoks RN 《Veterinary microbiology》2011,151(3-4):329-335
The molecular epidemiology of Pasteurella multocida has rarely been studied at the farm level in cattle. The aim of this study was to determine whether single or multiple strains of P. multocida tend to exist within farms. Molecular characterisation was carried out on isolates obtained from nasal swabs from 105 calves from 32 randomly selected beef and dairy farms located throughout Scotland, and from 131 calves from 20 farms in the Mayenne region of France, where sampling occurred in response to respiratory disease outbreaks. P. multocida isolates were characterised by random-amplified polymorphic DNA (RAPD) typing and pulsed-field gel electrophoresis (PFGE) using restriction enzyme ApaI. In addition, isolates representative of each farm/RAPD profile combination were typed by multilocus sequence typing (MLST). Among 105 Scottish isolates, 15 RAPD profiles were distinguished. The majority of farms (27/32) had indistinguishable profiles in all positive animals. Five farms had two profiles. Among 140 French isolates, 23 RAPD profiles were distinguished. More within-farm heterogeneity was observed although 10/20 farms had just one profile (E4) in sampled calves. Profile E4 accounted for 60% (84/140) of French isolates. PFGE was more discriminatory than RAPD but confirmed results with respect to within farm homogeneity or heterogeneity of strains, whereas MLST was not discriminatory enough for farm level epidemiology. As in other host species, either several strains or one dominant strain of P. multocida may exist within farms, with evidence for a role of management factors such as movements onto the farm in the number of strains detected. 相似文献
70.
CB Johnson KJ Stafford SP Sylvester RN Ward S Mitchinson DJ Mellor 《New Zealand veterinary journal》2013,61(6):433-437
AIM: To use the electroencephalogram (EEG) to ascertain whether the response of the cerebral cortex to the noxious stimulus of castration varied with age in lambs. METHODS: Two groups of East Friesian lambs were selected according to age; the mean age of the younger group (n=21) was 12 (SD 2) days and the older group (n=20) was 29 (SD 1) days. Anaesthesia was induced via mask using 4% halothane in oxygen, and maintained using 1.5% halothane in oxygen at a flow rate of 4 L/min. Once a stable plane of anaesthesia had been achieved, data collection of EEG and electrocardiographic (ECG) readings commenced, and the lambs were castrated 15 min later, using rubber rings. Median and 95% spectral edge frequencies (F95) and total EEG power (ptot) were derived from data from the EEG. RESULTS: Following castration, there was an increase in the median frequency (F50) in the younger lambs (p=0.002), and an increase in ptot in both groups (p=0.05), which was of greater magnitude in the older lambs. There were no significant changes in the F95. Both younger and older lambs exhibited a transient bradycardia (p=0.001 and p=0.01, respectively). CONCLUSIONS: These differences in the cortical response between the two groups suggest that 2-week-old lambs undergo a qualitatively different perception of the noxious stimulus of castration compared to 4-week-old lambs. 相似文献